1. Field of the Invention
This invention relates to construction of an inductor, and more particularly to construction of an inductor built into a printed circuit board.
2. Background Information
An inductance is often used as a filter inductance in series with a power source and a load in order to provide a high impedance for high frequency ripple current components in the current flow to the load, and a filter capacitor provides a short circuit for the high frequency current components to ground. The design of an inductor for use on a small printed circuit (hereinafter PC) board is a problem. Various solutions suggested in the art include, simply soldering a wire wound inductor onto the PC board, the use of a substantially circular trace in the PC board to form a one turn inductor as shown herein in FIG. 7, etc.
Difficulties encountered by all solutions suggested in the art include the cost and geometry of soldering a wire wound inductor to the PC board, the narrowing and hence higher resistance of a semicircular trace on a PC board, etc.
There is needed an improved way to make a filter inductor for a power supply mounted on a small PC board.
The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like reference numbers indicate identical or functionally similar elements.
The invention is an inductor formed by two substantially straight traces on a multilayer PC board passing through a ferromagnetic xe2x80x9cExe2x80x9d shaped core. The first trace is the positive output bus of the DC power supply, and the second trace is the negative output bus of the DC power supply. Sense lines used to sense voltage levels in the load are put through the same opening in the ferromagnetic xe2x80x9cExe2x80x9d core as the negative output bus trace. The sense lines are traces in a level of the multilevel PC board.